1. Field of the Invention
The present invention relates to a color image processing device provided in a copying machine, a printer machine, a facsimile machine and a scanner machine or the like. In particular, the present invention relates to a color image processing device which carries out a scaling processing or a spatial filtering processing of a color image.
2. Description of Related Art
A color image processing device provided in a printer machine and a scanner machine or the like includes an image processing circuit such as a scaling processing circuit for executing a scaling processing and a spatial filtering processing circuit for executing a spatial filtering processing on scanned color image data of an original document. Inside the color image processing device, a pixel value of each data of the color image data is expressed by a binary digit. For example, in case of color image data of a L*a*b* color system of eight bits, a pixel value of data of L* component (0 to 255), which takes only a positive value, is expressed by eight bits. A pixel value of data of an a* component and data of a b* component (−128 to 127), which takes both a positive value and a negative value, is expressed by code one bit and value seven bits.
Therefore, in a conventional color image processing device, as shown in FIG. 18, an image processing circuit, which executes a computation processing on the color image data of the L*a*b* color system, includes two computation processing circuits, i.e. a computation processing circuit 37 and a computation processing circuit 38. The computation processing circuit 37 executes a computation processing on the data of the color component, which takes only a positive value (the data of the L* component). The computation processing circuit 38 executes a computation processing on the data of the color component, which takes both a positive value and a negative value (the data of the a* component and the b* component). Then, among the color image data of the L*a*b* color system, a selection circuit 39 inputs the data of the L* component to the computation processing circuit 37 and inputs the data of the a* component and the b* component to the computation processing circuit 38. As described above, the data of the L* component and the data of the a* component and the b* component are processed by two computation processing circuits 37 and 38.
Another conventional color image processing device can process data of each of color components of color image data of a L*a*b* color system by one computation processing circuit. As shown in FIG. 19, an image processing circuit of the conventional color image processing device includes one computation processing circuit 40 which can process data of nine bits. The computation processing circuit 40 can process the data of all of the color components of the data of the L* component of eight bits and the data of the a* component and the b* component expressed by code one bit and value seven bits. Each of the data of the L* component, the data of the a* component and the data of the b* component is input to the computation processing circuit 40. In the computation processing circuit 40, a computation processing such as a scaling processing and a spatial filtering processing is executed on the color image data composed of the data of the L* component, the data of the a* component and the data of the b* component.
However, in the conventional color image processing device shown in FIG. 18, the computation processing is executed separately on the data of the color component, which takes only a positive value, and the data of the color component, which takes both a positive value and a negative value. Therefore, two computation processing circuits, i.e. the computation processing circuit 37 and the computation processing circuit 38, are required to be provided in the image processing circuit. Thus, there is a drawback that a hardware configuration of the image processing circuit becomes large.
In the conventional color image processing device shown in FIG. 19, both the data of the color component, which takes only a positive value, and the data of the color component, which takes both a positive value and a negative value, can be processed in one computation processing circuit. However, to process both of the above-mentioned data by one computation processing circuit, a bit number of the data, which can be processed by the computation processing circuit 40, is required to be set larger than the computation processing circuit 37 or the computation processing circuit 38. Thus, there is a drawback that in the conventional color image processing device shown in FIG. 19, a hardware configuration of the image processing circuit becomes large as in the conventional color image processing device shown in FIG. 18.